MOSLER GT300
specified catalytic converters, but no silencers. The long inlet trumpets and
the requirement to retain the standard engine inlet location called for a bespoke airbox, which, together with the rear wing, was laid up by carbon composite experts, Reverie, from moulds machined in tooling block directly from a CAD model by Concept Tooling. The suspension layout was
The position of the airbox required a bespoke design, which was modelled in CAD and laid up by carbon composite experts Reverie
carried over from the GT3 Mosler. ‘We could have gone to pushrod suspension but we tried to stick basically with what we knew, given the timeframe and knowing the ‘standard’ car handled nicely. It also eased the parts supply issue, as we started out thinking this would be a one off…’ said Short.
Cranfield graduate Ling Xiao refined the 3D CAD model so it could be run through CFD, a process that greatly sped up the design stage
Double wishbones front and rear are used with outboard spring dampers
COST-EFFECTIVE AERO Following a visit by the writer that highlighted areas where the Mosler’s aerodynamics would benefit from closer attention, Short contracted TotalSim to carry out a CFD analysis and optimisation project. ‘We had taken on Ling Xiao, who had just gained his motorsport engineering MSc from Cranfield, and he took this project on at our end, refining our 3D CAD model so it could be run through CFD. And as a cost saver he made the geometry changes recommended by the TotalSim engineers on the fly at TotalSim’s offices. Between them, TotalSim, Ling and the project leaders at Mosler – Michael Tallentire and Luke Kendall – worked through the JAF GT300 regulations and came up with some new ideas, such as the box sections on the rear wings (fenders), which hadn’t been used in the series before. Ling’s 3D skills were essential to this project. The car probably wouldn’t have happened on time without his hard work. ‘We checked everything with
CFD project undertaken with TotalSim yielded benefits. Here we see streamlines viewed from the front of the car
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www.racecar-engineering.com • September 2011
the JAF, who were very helpful and gave us the nod on our new ideas. They even commented on the rear wing being quite low and asked if we wanted to raise it. But its profile, which we designed, was optimised for the regulation height. It might have been useful to know earlier that we could have raised it though… At times, the regulations did
seem to be a moving target, but Raja and the JAF worked together well, and we got through all the issues,’ explained Short. The team had originally drawn
up a pair of large front diffusers, aft of which the chassis featured a ship’s bow-shaped divider ahead of the front compartment rear bulkhead. The CFD project showed that even with exits aft of the front wheels, the bulkhead was preventing effective air egress and that a simpler, smaller front diffuser set up actually performed better. Further gains were found with a shaped radius on the splitter leading edge. To avoid the use of costly composites in this vulnerable component, the splitter was made from a marine ply upper half and Jabroc lower half. Other details around the wheel wells and rear bodywork produced worthwhile gains in downforce, with overall a drag reduction compared to the GT3 car.
DOUBLE CRASH TEST The mandatory crash tests were carried out at the Cranfield Impact Centre in the UK, and so great were the energy requirements that the test had to be done in two hits, literally, and the combined results added together. It passed. Unsurprisingly, considering Short’s original business was manufacturing racecar rollcages, the tubular spaceframe was made in-house. ‘It’s probably over engineered,’ he admits ‘but we knew from a TVR Cerbera we built and ran in 1999 that there’s nothing wrong with an ‘old tech’ spaceframe, you can get massive torsional rigidity numbers.’ The standard Mosler features a carbon composite chassis with front and rear subframes bolted to this, and the expectation was that losing these bolted joints, combined with better load paths, would increase overall chassis stiffness.
EARLY RUNNING The timeframe proved too tight to make the first JAF Super GT race in spring 2010 (parts supply being the main delaying factor) but, after a shakedown test at Silverstone, the car made it to Japan for the second race. It was there the woeful lack of engine
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